Vibrating Structure Gyroscope sensing element structures are conventionally driven resonantly on the cos2.theta. mode with the ring or cylinder motion as shown schematically in FIG. 1 of the accompanying drawings over a single cycle. There are two modes of vibration supported on the ring or cylinder at a mutual angle of 45.degree. as shown conventionally in FIG. 2 of the accompanying drawings in which the primary mode is shown at 1 and the secondary mode is shown at 2. For a perfectly symmetric structure the resonant frequencies of the two modes will be degenerate. However in practical devices there exists a frequency split (.DELTA.f) due to imperfections in the structure and material. These imperfections will lock the position of the vibration modes on the structure and in order to achieve optimum performance it is necessary to match these two frequencies to enable energy to couple efficiently between them.
One method has been proposed for balancing the frequencies of the primary and second modes of vibration by the controlled removal or addition of material from the resonant structure. Whilst this system is effective anisotropies and material imperfections will cause the frequency split (.DELTA.f) to vary with temperature. The scale factor and bias terms are directly influenced by the frequency split and will thus show temperature dependence. There is thus a need for a method for actively balancing a vibrating structure gyroscope sensing element structure of ring like or substantially cylindrical form made of ferromagnetic material.